Combination generator for an electronic postage meter

ABSTRACT

Apparatus in a microcomputerized postage meter internally generates a finite set of combination of numbers having a specifiable number of digits in each combination. The combinations are used to allow for the addition and removal of postal funds within the meter. The apparatus utilizes a modification of common coding schemes to implement the generation of the combinations. The modification provides for the generation of an intermediate combination of numbers from a seed table located within the postage meter. The modification thereafter provides for the generation of the internally generated combinations from the intermediate combination. Thus, the internally generated combination is generated by using existing code. By use of this modification, less memory capacity is necessary to store combinations than with previous combination generation schemes, thereby allowing for that capacity to be used for other functions within the postage meter.

FIELD OF THE INVENTION

This invention relates to security systems and more particularly to thesecurity systems associated with electronic postage meters.

BACKGROUND OF THE INVENTION

It is important in postage meters that the meter be physically securefrom intrusion. As is well known, postage meters can be recharged; thatis, additional value can be added to them in a variety of ways. Forexample, the postage meter can be physically taken down to a Post Officewhere the Post Office personnel will physically add incremental amountsof value to the meter or remove funds from the meter. Often times, themeter will have a external lock of a mechanical variety that is openedby a key. In addition, postage meters of this type have a combinationassociated therewith to allow for additional funds to be added to themeter. The combination adds additional security to the postage meter andprevents unauthorized personnel gaining access thereto.

It is important in this kind of system that the security be enhanced andthereby have a combination associated therewith in which only theauthorized user can gain access. There are several existing methods forsecuring these kinds of meters from unauthorized personnel. Thesemethods are generally effective but it is important to continue todevelop new and better ways for securing the meters.

Often times, the Post Office will want to have the ability to change thecombination generated by a microprocessor or the like to preventunauthorized access to the postage meter. This capability is importantin as much as personnel within the Post Office ma change thereby incertain circumstance, making it desirable to change the new combinationnecessary to unlock the postage meter. The ability to change thecombination is important also because, since as is well known, postagemeters are often leased to customers, the customers should not have theability to open the meter at any time even if they somehow gained accessthereto.

It is well known that schemes are used in a hotel to periodically changethe locks. For example, if a customer uses the key to a hotel room andthen inadvertently or purposely takes the key upon checking out of thehotel, there are schemes which will allow the hotel manager to give thenext customer a new key thereby changing the lock or combination of thelock and allowing the new owner or the new customer access to the room.At the same time, the old key taken by the previous customer will nolonger open the door. As before mentioned, this scheme is used toprevent unauthorized personnel from gaining access thereto. For hotellock systems, there should be a set of combinations generated forimplementation of the above-mentioned scheme. This can be accomplishedin a variety of ways.

Similarly, in a postage meter, a desirable system should be providedthat can perform a function very similar to that performed in theabove-mentioned hotel system; that is, providing a set of combinationsthat will in a sequential manner provide access to the postage meterafter using a physical key.

Thus, it is important in a manual recharging type postage meter to havemeans for generating a set of combinations in a simple and efficientmanner to allow for enhanced security. At the same time, thesecombinations should desirably be generated in a random-like fashion sothat it will not be easy to recreate the combination and thereby enterthe locked postage meter.

A postage meter which uses series of combinations to unlock the meterfor funding is disclosed in U.S. Pat. No. 4,097,923 in the names ofAlton B. Eckert, Jr., Howell A. Jones, Jr. and Frank T. Check, Jr.,assigned to the assignee of this patent application. In Eckert et al,there is disclosed a remote postage meter charging system using anadvanced microcomputerized postage meter. This system is built around amicrocomputer set and the meter contains seed numbers for generatingpostage funding combinations. The remote postage meter charging systemhas the capability of adding variable amounts of postage into thepostage meter.

Another type of postage meter that will need a combination of numbersgenerated for it is a microcomputerized postage meter that does not haveremote postage charging; that is, a postage meter that has amicrocomputer within it that it also is physically under a mechanicallock and key. In addition to the mechanical lock, a series of numbersmust be entered into the postage meter must be entered to open thepostage meter to allow funding. This type of postage meter as beforementioned has to either be taken physically down to the Post Office orpersonnel must visit the customer's premises to allow the additionalfunding to take place.

Thus, it is important that in this kind of meter that an individual whohas the key to the mechanical lock also has the combination to add thefunding to the meter. In manually recharged kinds of meters that arephysically carried to the Post Office or where authorized Post Officepersonnel comes to customer's business, again a combination isinternally generated to unlock the meter.

Also, in postage meters of this type, the meter's combination should besecure to prevent unauthorized entry into the postage meter. Heretofore,there have been methods and apparatuses for generating a series ofcombination of numbers within the postage meter. Prior systems haveprovided adequate security and have operated satisfactorily. However,often times, the apparatus utilized in postage meters, such as thoseused in remote recharging postage meters to generate the combinations,are complex and expensive. In addition, these schemes often timesrequire the use of valuable memory space in the postage meter. Thus,what is desired is a way of internally generating series of combinationsin a microcomputerized postage meter that will allow for a random orpseudo random pattern and also reduce the amount of valuable memoryspace used in the microprocessor that heretofore has been necessary.

SUMMARY OF THE INVENTION

Apparatus provide a series of combinations of numbers for an electroniclock system for an electronic postage meter. These combinations willprovide a postage meter with a series of numbers that can be utilized toadd or remove postage funds within the meter. More particularly, withoutthe proper combination of numbers, the unauthorized personnel cannotgain access to the postage to add funding thereto.

This apparatus is used advantageously in a microprocessor based postagemeter. In this system, the postage meter responds to a set of numbers tounlock the device to prevent unauthorized entry to the postage meter.Stored within the postage meter are a seed and a program which produce afinite series of combinations. The number of digits in each combinationis specified by a number stored in the meter which may vary from meterto meter. The combinations produced by the postage meter are utilized insuch a manner that the meter responds to two combinations, the primaryand the secondary combination, until such time that the last combinationin the finite series of combinations has become the primary combinationand no secondary combination exists. The primary combination may be usedas often as desired without causing a change in the primary or secondarycombinations. Use of the secondary combination, in addition to allowingaccess, causes the secondary combination to become the primarycombination and causes the next combination in the series, if oneexists, to become the secondary combination.

In accordance with one embodiment of the invention, an apparatus isdisclosed that will internally generate a finite number of combinations.This apparatus comprises means for generating a sequence of aspecifiable number of digits forming a combination, that combinationbeing dependent upon the combination sequence number, the number ofdigits specified for the combination and a table of seed numbers in thememory location of the microprocessor. This apparatus includes a routineusing the above-mentioned functions to generate an intermediatecombination from the seed table which is equal in size to the seedtable. Thereafter the same routine is utilized with the intermediatecombination instead of the seed table to generate a combination with thespecified number of digits that is to be used to unlock the postagemeter.

In accordance with this embodiment, a routine already existing in themeter which generates a cyclical redundancy code (CRC) is used as partof the routine to generate the combination. The CRC values generated areused by other routines to provide a finite number of combinations. Thisapparatus saves valuable memory space, in the microprocessor because thetables are generated through calculation rather than being part of theoverall memory of the system thereby allowing for memory space to beused for other purposes. These combinations can thereafter be usedsequentially to provide the numbers for unlocking microprocessor basedelectronic postage meters and the like. This apparatus is a simple wayto generate a finite number of combinations for a microprocessor basedpostage meter while using an existing coding scheme.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a microcomputerized postage meter.

FIG. 2 shows in block diagram form the interaction of the electroniccircuitry within the postage meter.

FIG. 3 is a perspective view of a general housing arrangement of themeter of FIG. 1.

FIG. 4 is an enlarged plan view of the front panel of the postage meter.

FIG. 5 is a generalized flow chart of a routine for generating a seriesof combinations to be used in conjunction with postage meters similar tothat of FIGS. 1 and 2.

FIG. 6 is a flow chart of a subroutine MANCLK which is associated withthe generalized flow chart of FIG. 5.

FIG. 7 is a flow chart of a subroutine MANCMB which is associated withthe subroutine generalized flow chart of FIG. 6.

FIG. 8 is a flow chart of a subroutine MANALG which is associated withthe subroutine flow chart of FIG. 7.

DETAILED DESCRIPTION OF THE DRAWING

FIG. 1 shows a perspective view of a microcomputerized postage meter ofthis invention. As will be described in further detail hereinafter, apostage meter 100 has a keyboard 34 for entering data into andcontrolling the operation of the meter. Postage is funded into the meter100 by opening the base of the meter 100 via a key (not shown). The PostOffice personnel provides the identifying number of the meter 100 to befunded. The last readings of the ascending and descending registers ofthe meter 100 and the amount of postage which is desired to be enteredinto the meter 100 are noted. The Post Office personnel then unlocks themeter 100, keys in the desired postage on the keyboard 34 and enters thecombination. The meter 100 contains an apparatus which then generates aninternal combination.

The meter 100 is recharged with the previously keyed in postage amountif the combination entered is in agreement with the internally generatedcombination. The apparatus which generates this combination will bedescribed in greater detail hereinafter.

Referring to FIG. 2, the general functional arrangement of themicrocomputerized postal meter 100 of the present invention is shown.The heart of the system is a central processing unit CPU 201 and itperforms two basic functions: performance of calculations based on inputdata and controlling the flow of data between various memory units.Three basic memory units are employed by CPU 201. The first is thepermanent memory (PM) 202 which is a non-alterable memory storing aspecific sequence of operations for performing postal data calculationsin occurrence with certain predetermined inputs as well as performingother routines for operating the system. A second memory unit is atemporary memory TM 203 which interacts with the CPU 201 for forming atemporary storage holding and forwarding working data in accordance withthe calculation being performed by the CPU 201. An additional memorycomponent NVM 204 is also coupled to the CPU 201 and performs a storagefunction which is very significant in this system's operation of apostal data system. The NVM 204 is a non-volatile memory which acts tostore certain critical information employed in the postal system as partof a predetermined routine activated either upon shut-down or start-up.The NVM 204 contains variable data that must be preserved in the eventof the loss of electrical power.

A routine located in the permanent memory PM 202 is accessed by anappropriate sensing device for sensing either of two steady conditions(shut-down or start-up) for operating the CPU 201 in accordance withthat routine. The function of this routine is to take information storedin the temporary memory 203 which represents the result of crucialaccounting functions such as descending balances or extending creditsand the like and store them in the NVM 204 where they may be held whilethe machine is de-energized and recalled upon subsequent start-up. Inthis manner, the computer system may continually act upon the balancesin temporary memory without fear of loss of this information uponshut-down.

Further, the information may be recalled on reactivation by start-up byretrieving it from the non-volatile memory 204 and feeding it back intothe TM 203 via the CPU 201. The non-volatile memory 204 is shown ascoupled to CPU 201 and deriving an output therefrom in accordance withthe transfer of information from the temporary memory 203 under thecontrol of the permanent memory 202 through the CPU 201 in accordancewith the shut-down routine.

The NVM 204 is also shown as providing an output line coupled back intothe CPU 201 for transferring the data back into and through the CPU 201and into the temporary memory 203 in accordance with the start-uproutine under the control of the permanent memory 202. The systemoperates in accordance with data applied from an appropriate input meansI 205. This data is fed into the CPU 201 under control of the program inthe permanent memory.

At any time during the operation of the system should the contents ofthe temporary memory 203 storing the appropriate credit, debit, balancesor other accumulations in accordance with the various features of thissystem be desired to be displayed, appropriate instruction provided bythe input means 205 causes the CPU 201 to access the desired location TM203 storing the information requested. The information is providedthrough the CPU 201 into the output display O 206. The input 205 andoutput 206 units may be multiplexed by a multiplex unit MP to and fromthe CPU 201.

Under control of the CPU 201, when appropriate postal data informationis provided from the input 205 and all the conditions such as limits andthe like which may be preset in accordance with the entered data andstorage in the temporary memory 203 are satisfied, a postage settingdevice SP 207 will respond to an appropriate output signal from the CPU201 enabling a postal printing unit PP 208. At this point, the systemnow has accomplished its immediate function of setting the postageprinter enabling the printer to print postage. The foregoing functionaldescription of the present meter and its embodiment is described in fulldetail in U.S. Pat. No. 4,097,923 issued on June 27, 1978 in the namesof Alton B. Eckert, Jr., Howell A Jones, Jr. and Frank T. Check, Jr.

Referring to FIG. 3, there is shown a general housing arrangement forthe microcomputer postage meter. The housing arrangement comprises ahousing 100 that contains a module plug-in circuit panels 101 containingcircuitry in the CPUs, ROMs and RAMs and shift registers of the meter.The keyboard 34 and display 35 are mounted on the common top panel 102of the housing 100. The setting and printing mechanism is contained in aforward section generally shown by the arrow 103. An envelope 104 whichis to be printed from postage is introduced into the slotted portion 105of the meter section 103 after the meter is initialized. The amount ofpostage to be printed is then keyed into the keyboard 34 via pushbuttons107. The set button 119 is pushed to set the postage into the print drumand the print button 108 is depressed. The print button 108 may bereplaced by limit switch or optical sensor located in slot 105 whichwould automatically provide a print signal when an envelope enters slot105.

FIG. 4 is an enlarged view of panel 102 of FIG. 2 which contains thekeyboard 34 and display 35 of the postage meter. The keyboard 34comprises pushbuttons 107 as aforementioned to enter the numericalamount of postage into the system. Pushbuttons 109, 110, 111, 112, 113and 114 cause the numbers stored the electronic registers for batchcount, batch amount, piece count, control sum, ascending register anddescending register, respectively to be displayed. When any one of thesebuttons are depressed, the numerical section 115 of the display, iscleared, the appropriate register is loaded into the the numericalsection 115, and the appropriate indicator lamp 131-136 in section 116of the display is lighted. Lamp 128 is lit to indicate that the postagemeter is ready for operation.

The keyboard 34 and display of this invention provide two new registers(more can be added without too much difficulty). Batch count and batchamount registers supply a running account of the total number of piecesof mail processed and total postage expended, respectively, during anyone run or time period. They can be reset to zero by the user.

The control sum register is extremely useful in that it provides a checkupon the descending and ascending registers. The control sum registerhas a running account of the total funds being added into the meter. Thecontrol sum register must always correspond with the summed readings ofthe ascending and descending registers. The control sum register is thetotal amount of postage ever put into the machine and it is alterableonly when adding funds to the meter. Generally, mechanical meters arenot resettable by the user but only by postal authority. It is also truefor electronic postage meters that often times postal authorities wantthe meter to be only resettable by that authority. The piece countregister differs from the batch count in that it is not resettable bythe user and it is used to indicate the total number of postageprintings the machine has experienced. This information is useful toascertain the life of the machine and to gauge when the system mayrequire servicing and maintenance.

The ascending and descending registers operate in a normal fashion thatmight be expected from a standard postage meter. The ascending registergiving a running total of the printed postage and the descendingregister informing the operator of the amount of postage funds stillremaining in the postage system. The key pushbutton 117 provides afunction of addition for adding in special charges to the postage suchas the special delivery, certification, etc. The clear key 118 clearsthe numeric display 115 and also sets the batch register to zero. Ifeither one is displayed at the time, the clear key is actuated.

The set button 119 is depressed after the postage required to mail aletter is keyed in by buttons 107. The set button 119 causes theprinting wheels in a printing drum (not shown) of the postage meter 100to set the desired postage. The dollar unlock lamp 130 warns thatpostage over $1.00 has been keyed in. The dollar unlock key 120 is aprecautionary button which may be depressed by the operator in order toset postage equal to or in excess of a dollar. This extra physical stepacts to prevent costly postage printing mistakes. The need to add fundsto the meter 100 is signaled by indicator lamp 137.

Funds are added to the meter 100 by obtaining a key that can be insertedin the key way of lock switch 121. The switch is now free to be turnedto a first position and a indicator light 122 is lit. Light 122instructs the operator to key in the funding amount into the keyboard 34via pushbuttons 107. After the funding amount is entered, the switch 121is turned to a second position. Light 123 instructs the operator toenter a combination. A number sequence comprising an unlockingcombination is then entered into the meter using pushbuttons 107.

The switch 121 is now turned to a third position. The turning of theswitch to this third position will evoke one of the two responses fromthe system. If the combination is a valid one, then the indicator lamp124 will light to inform the operator that the entered combination is acorrect one. The key should be removed from the lock switch 121. If, onthe other hand, however, the entered combination was incorrect,indicator lamp 125 will be lit to inform the operator of this fact andto instruct him to repeat the funding procedure.

It is desirable that the internal combination be changeable to furtherenhance the security of electronic postage meters. Often times, postalemployees may leave the employment of the Post Office. Upon thatoccurrence, it may happen that the key that is used to unlock the keyswitch on the postage meter will be taken by that personnel. The PostOffice will therefore want to change the combination of a postage meterwhen that employee leaves.

Therefore, it is important that there be a series of combinationsgenerated within the postage meter whereby if one combination has beencompromised then another combination can be substituted therefor. Infact, in a situation where initially a first combination is utilized,then if for some reason that combination is compromised, the secondcombination will be utilized and the initial combination will no longerbe able to open the postage meter or to add additional funding to thepostage meter.

Generally, these combinations can be either stored or generated in avariety of ways. Often times, tables of values are located within one ofthe memory locations (FIG. 2) of the postage meter to provide the propercombination. In this kind of scheme, the CPU 101 would thereupon "lookup" the particular value. This type of procedure would require the useof large amounts of memory space to store the series of combinations.Thus, what is done in this invention is to store a small table of seednumbers in the memory location (probably NVM 204) which serves todifferentiate one meter from another and to generate the combinationsutilizing a subroutine which is the same from meter to meter and residesin the less expensive permanent memory.

The operation of multiplication is commonly used in subroutines whichproduce a series of random digits from a given seed. However, since nocode to perform multiplication exists in the meter, a method of randomdigit generation based on an existing cyclic redundancy code (CRC)generator was created. There are a variety of CRC schemes that can beimplemented to provide the numbers. CRC schemes are well known. Theenhanced security is provided by the present invention by not utilizingCRC schemes exclusively to generate the combinations. Thus, it isappropriate to utilize an existing CRC generating scheme as arandomizing means in conjunction with additional coding to generate thecombination of numbers in such a way that someone familiar with the CRCcoding would not readily break it.

In this invention, Applicant provides such a coding scheme to enhancethe security of the postage meter. This improvement will be described byreferring to FIGS. 5 through 8 in association with the followingdiscussion. At the outset it should be noted that although thisinvention is described in terms of a particular method of CRC generationin conjunction with particular additional code, it is done forillustrative purposes only. Thus, this invention could be utilized withother methods of number generation and similar forms of the additionalcode and those teachings would still be within the spirit and scope ofthe invention.

In accordance with the embodiment of the invention, the flow chart ofFIG. 5 shows in generalized form a routine for manually resetting thepostage meter indicated by MAN RESET 94. As shown in the figure, adecision box 95 indicates whether a combination is necessary to open themeter or not. If a combination is not necessary and only a key isrequired to open the meter for funding then the routine MANNLK 96(manual no lock) is implemented which will allow a key to open themechanical lock manually. If the decision box 95 indicates that acombination is necessary to open the meter then the routine MANCLK 97(manual combination lock) is entered. This routine initiates the schemeof generating the combination. As is seen in the figure, after eitherthe MANCLK 96 or MANNLK 97 is processed without error, then postagefunds have been entered into the meter.

By way of explanation, certain terms will be defined to add clarity tothe foregoing description. A value as described in this application is abinary number containing any number of bits. A digit as described inthis application is a 4 bit binary value variously interpreted toinclude hexadecimal values .0. through F, binary coded decimal (BCD)values .0. through 9, and octal values .0. through 7. A singlecombination is a group of digits. That group can be of any digit length.A table as will be hereinbelow described is a collection of a certainnumber of digits in which a single combination can be derived or aplurality of combinations can be derived. The number of digits in acombination can be specified by the non-volatile memory located withinthe electronic postage meter.

FIG. 6 shows the routine MANCLK in more detail. The object of thisroutine is to generate a finite number of combinations containing aspecifiable number of digits. The number of digits is specified by avalue located in the non-volatile memory. If the locking device is in astate S where S is the sequence number of the current primarycombination greater than zero but less than N, N being the sequencenumber of the last combination in the finite series of combinations,then the locking device is responsive to the (S)^(th) combination andthe (S+1)^(th) combination. If S equals N, then the device is responsiveto only the N^(th) combination. This is one variety of the hotel lockscheme referred to in the figure. MANCMB, box 300, generates the(S)^(th) combination which is outputted to a decision box 301. Thedecision box determines whether the externally entered combination valueblock 290, matches the combination that is to be used to enter fundsinto the meter.

If the combinations do match, then program execution follows the trueleg down to MANAMT, 302. The externally entered amount from block 280 isthen added to the descending register if the amount is within suitablelimits and the routine is exited at box 309. If the flag is false fromdecision box 301, then another decision box 303 is entered. Thatdecision box 303 tests the relationship between S and N to determinewhether there is a secondary combination. If S=N, then there is nosecondary combination and the routine is exited at box 309. If there isa secondary combination, MANCMB 310 is executed again to calculate(S+1)^(th) combination. This combination is then compared with theexternally entered combination at decision box 306. The decision box 306if false will cause the routine to quit. If the flag is true, however,then MANAMT 307 is entered. If the externally entered amount is withinsuitable limits, then the money is added to the descending register. Theerror flag output by MANAMT will be true if the entered amount could notbe added to the descending register. The flag is tested in decision box308. If the amount was successfully added to the descending registerthen at 311 the (S+1)^(th) combination becomes the (S)^(th) or primarycombination. In any event, the routine quits box 309.

The above discussion describes how the hotel lock routine is utilized toproceed from one combination to the next in this embodiment. Thus, ascan be seen from FIG. 6, there is a possibility that MANCMB will beexecuted twice to determine whether a combination is the primarycombination or the secondary combination.

FIG. 7 shows the routine MANCMB in more detail. The object of MANCMB isto generate one of a finite number of different combinations which is afunction of the sequence number of the combination, the number of digitsin the combination and the seed number table stored in the particularpostage meter. Seed numbers are utilized in microcomputerized postagemeters and are also utilized in random number generation schemesassociated therewith. Typically, each postage meter will have its ownset of seed numbers. In this routine as shown in FIG. 7, another routinecalled MANALG 401 s executed under instruction that the seed numbers areto be used as the generating table to produce an intermediatecombination. This combination can be of any digit length and in thiscase the intermediate combination is the same size as the seed table.Thereafter, MANALG is called again (box 403) under instruction that theintermediate combination is to be used as the generating table toproduce a second combination. This is the combination that will open thepostage meter. After the second combination is produced, the routine isexited at 405.

Referring to FIG. 8, the routine MANALG is shown in more detail. MANALGgenerates a more or less random sequence of a specifiable number ofdigits as a function of a sequence number, the specified number ofdigits and a specifiable table of values. The routine MANALG can beadapted to an existing coding scheme to produce the sequence of digits.In this embodiment, a CRC scheme is used by the routine to produce therandom sequence of digits. Those skilled in the art recognize othercoding schemes can be utilized and still be within the spirit and scopeof the invention.

The MANALG routine also insures that the first digit of the randomsequence is odd or even as the value of the sequence number of thecombination is odd or even. Thus, providing that succeeding combinationsare not identical. Once again, however, it is clear that thecombinations can be varied in another way such as changing the lastdigit in variance with sequence number, and still be within the spiritand scope of the invention.

Referring again to FIG. 8, Box 500 shows the initializing step for thedifferent functions of the combinations. In this embodiment, thesequence number and the number of digits of the combination are alreadydefined. In an initializing procedure indicated by Box 501 CRCVAL is setto some value. Then the sequence number is accumulated into the CRCVALby the statement as shown in Box 502. CRCNIB is a function that willtake the sequence number and accumulate it in a special way into thevalue of CRCVAL. CRCNIB contains a well known algorithm which isutilized extensively by those skilled in the art.

The statement IN=0, Box 503 indicates the input subscript to indicatewhich digit of the table is being referenced. For example, in thisembodiment, each digit is 4 bits in length. Thus, for each digit, thesubscript value of IN would correspond to each set of 4 bits in asequential manner. Box 504, sets the number of digits that will beproduced in the combination. Thus, the digit counter (DGTCTR) can be,for example, between 1 and 16 digits as defined thereby by the constant(DGTCNT) which is established when the meter is manufactured. Finally,OUT=0, Box 505 is another subscript that indicates which digit of thecombination is being calculated.

The outer loop 520 of the flow chart of FIG. 8 will be repeated for eachdigit of the combination as will be hereinafter described. The innerloop 521 is repeated a variable number of times dependent upon the valueof LOPCTR, a loop counter, whose value depends on intermediate values ofthe developing CRC.

Initially, LOPCTR, 507, is equal to the CRCVAL with an operationperformed on the CRCVAL number. For example, the CRCVAL can be "anded"with a hex value to produce a number. This number controls the number oftimes that box 512 is executed. Box 509 provides for producing an inputsubscript which is a function of CRCVAL, the previous value of IN andanother operation performed on the number. As before mentioned, IN isinitially 0 (Box 503). As can be seen, this operation causes IN to bevarying in a non-sequential manner as a function of other varying values(CRCVAL and the operations). Thereafter, in Box 510, a new CRCVAL isproduced by use of the CRCNIB routine in conjunction with a digit fromwhatever table is specified. The table can be of 64 bits or some otherfinite number. Then, the loop counter is decremented as indicated by Box511. For each digit, loop 521 will be repeated some variable number oftimes until the value of loop counter is less than zero.

As shown by decision Box 513, if the loop counter, LOPCTR, is greaterthan or equal to zero then, the above-mentioned operations are repeated.If however the loop counter, Box 511, is less than zero, then the digitof the combination is calculated by Box 514.

Box 515 indicates the incrementing of the output subscript. If there aremore digits to be calculated; that is, if DGTCTR is greater or equal to1 then looping back to 506 via 520 continues with the production of thenext digit. If the combination has the requisite number of digitsrepresented by DGTCTR less than 1 then, in box 519, the first digit ofthe combination is made odd or even as the sequence number of thecombination is odd or even, and a combination has been generated toallow funding to the postage meter. Thus, as can be seen from thisarrangement, the combination can be of any length dependent upon thevalue initially within DGTCNT.

Thus, by calling the MANALG routine of FIG. 7 twice by the use of theMANCOMB routine of FIG. 6, a random sequence of numbers are generated toproduce a set of combinations. The combinations are generated utilizinga seed table stored in the meter and generating those combinations fromthe table. Thus, the combinations are not actually stored in the meterbut are generated on a "as needed" basis. This allows for a savings inmemory capacity thereby allowing for that unused memory space to beutilized more efficiently in storing other critical information.

Thus, by the use of the two routines, MANCMB and MANALG, a combinationis produced from a table of seed numbers. The routines therefore providea means of generating a combination from a finite set of numbers ratherthan storing a table of combinations within the memory locations of thepostage meter. Also, the use of the routines allow for combinations ofnumbers to be of varying lengths to be generated from these tables.

This is important because memory space, especially the non-volatilememory of the postage meter, is very valuable because of limited memoryspace for particular priced memories suitable for use in mass producedpostage meters. Thus, when it is possible to utilize less of the space,as is the case here, there is room to add other critical information tothe NVM and therefor more efficiently use the memory capacity.

The above-described embodiments can be modified in a variety of ways andthose modifications would still be within the spirit and scope ofApplicant's invention. Thus, while this invention has been disclosed bymeans of specific illustrative embodiments, the principles thereof arecapable of a wide range of modification by those skilled in the artwithin the scope of the following claims.

What is claimed is:
 1. A postage meter comprising:means for entering aselected amount of postage into the postage meter in preparation forfunding the meter with the postage amount, means for internallygenerating a set of unique combinations to allow funding the meter, theinternally generating means having a table of seed numbers, theinternally generating means further comprising: means for producing anintermediate combination from the table of seed numbers, and means forproducing the set of unique combinations in response to the intermediatecombination producing means, means for entering an externally generatedcombination into the postage meter, means for comparing a plurality ofthe unique combinations of the set of internally generated combinationswith the externally entered combination, and means for funding thepostage meter with the selected postage amount when the comparisonindicates the existence of a predetermined relationship between theplurality of the unique combinations of the set of internally generatedcombinations and the externally generated combination.
 2. The postagemeter of claim 1 in which the intermediate combination producing meansand unique combination producing means each comprises means for encodinga digit into a value and means responsive to the encoding means forcombining multiple encoded values into a sequence of a specifiablenumber of digits.
 3. The postage meter of claim 2 wherein theintermediate combination producing means and the unique combinationproducing means each further comprises:means for performing apredetermined operation on the values produced by the encoding means,and means for controlling the number of times the performing means isactivated, the controlling means activating said performing means saidnumber of times as a function of a sequence number of a table of valuesand a value specifying the number of digits in the combination.
 4. Thepostage meter of claim 2 in which the encoding means uses a cyclicalredundancy code for encoding the digit.
 5. The postage meter of claim 1wherein said means for comparing compares two unique combinations withthe externally entered combination, the postage meter including meansfor replacing an unselected one of the two unique combinations withanother unique combination for use in a next comparison when thecomparison indicates the presence of the predetermined relationshipbetween a selected one of the two unique combinations and the externallygenerated combination.
 6. A method for funding a postage metercomprising the steps of:entering a selected amount of postage into thepostage meter in preparation for funding the meter with the postageamount; generating within the postage meter an intermediate combinationutilizing a table of seed numbers; producing a set of unique postagemeter combinations in response to the generation of said intermediatecombinations; entering an externally generated combination into thepostage meter; comparing the externally generated combination with aplurality of the unique combinations of the set of postage metercombinations, and funding the postage meter with the selected postageamount when the comparison indicates the existence of a predeterminedrelationship between the externally generated combination and theplurality of unique combinations of the set of postage metercombinations.
 7. The method of claim 6 wherein two unique combinationsare compared with the externally generated combination, and when thecomparison indicates the presence of the predetermined relationshipbetween a selected one of the two unique combinations, the unselectedcombination of the two unique combinations is replaced with anotherunique combination for use in a next comparison.